Through electrode, spacer provided with the through electrode, and method of manufacturing the same

ABSTRACT

A through electrode that offers excellent performance and can be manufactured through a simple process is to be provided. In a silicon spacer including a silicon substrate, an insulative thick film is provided so as to be in contact with a surface of the silicon substrate and a side wall of a through hole penetrating the silicon substrate. An upper surface of a through plug is retreated to a lower level than an interface between the silicon substrate and the insulative thick film, thus to define a height gap. A first bump is then formed, which is connected to the retreated surface of the through plug and has a larger diameter than that of the through plug at the upper surface of the insulative thick film.

This application is based on Japanese patent application No.2004-099681, the content of which is incorporated hereinto by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a through electrode, a spacer providedwith the through electrode, and a method of manufacturing them.

2. Related Art

In recent years, with the view of achieving an even higher degree ofintegration of a semiconductor chip, development of three-dimensionalimplementation of semiconductor chips such as an LSI has lately beenvigorously carried out. Such attempts include providing a throughelectrode on a semiconductor substrate. An example of the throughelectrode is disclosed in the H. Yonemura, et al., “Time-ModulatedCu-Plating Technique for Fabricating High-Aspect-Ratio Vias forThree-dimensional Stacked LSI System”, 2002, Proceedings of theInternational Interconnect Technology Conference, pp. 75 to 77 (H.Yonemura, et al.). The document discloses a through electrodeconstituted of a Cu plug formed so as to penetrate a silicon substrate,with a bump formed on an upper face of the Cu plug. Providing suchthrough electrode allows achieving electrical connection between thesubstrates and an external component via a short distance without theneed of performing wire bonding, when three-dimensionally stacking aplurality of semiconductor chip substrates.

SUMMARY OF THE INVENTION

However, as a result of the review on the cited technique made by thepresent inventors, it has now been discovered that sufficient secure ofadhesion between a metal film and the bump constituting the throughelectrode has still room for improvement. In addition, a room forfurther simplification has been found in the manufacturing process ofthe through electrode.

According to the present invention, there is provided a throughelectrode comprising a silicon substrate provided with a through hole;an insulating protective film formed on a surface of the siliconsubstrate with an opening connecting with the through hole; a throughplug formed by embedding a conductive material in the through hole; anda bump connected to the through plug; wherein the bump is connected tothe through plug inside the through hole, and a portion of the bumplocated outside the through hole has a larger diameter than that of aportion of the bump located inside the through hole. In suchconfiguration, the bump may be connected to the through plug on thesurface of the substrate.

In the through electrode thus constructed, the bump is connected to thethrough plug inside the through hole penetrating the silicon substrate.This means that a recessed portion is formed on the silicon substrate,and it is in the recessed portion that the through plug and the bump areconnected. Also, the bump has a larger diameter outside the throughhole. Accordingly, the bump and the through plug are tightly adheredbecause of an anchoring effect. Further, the electrical contact betweenthe bump and the through plug is fully secured, which leads to decreaseof contact resistance therebetween. In addition, since the insulatingprotective film is provided, the bump can be kept from directlycontacting with the silicon substrate on the surface where the throughelectrode is formed.

In the present invention, the conductive material may be made of a metalmaterial. This further assures the conductivity of the throughelectrode.

In the through electrode according to the present invention, thelarger-diameter portion of the bump may be in contact with theinsulating protective film. Such configuration can keep the bump fromcontacting with the silicon substrate. This enhances the reliability ofthe electrode in its essential performance.

The through electrode according to the present invention may furthercomprise a side wall insulating film formed so as to cover a side wallof the through plug. Such configuration allows suppressing generation ofa parasitic capacitance in the silicon substrate along the sideperiphery of the through electrode. This further increases thereliability of the through electrode.

In the through electrode according to the present invention, the sidewall insulating film and the insulating protective film may becontinuously and integrally formed. Such configuration allowsmanufacturing the configuration by simple process.

The term “continuously and integrally formed” herein means forming acontinuous and unified structure. Preferably, the structure isconstituted of a single part without forming a joint portion. Forming acontinuous and unified structure allows preventing the side wallinsulating film and the insulating protective film from separating ordetachment from each other. Accordingly, such constitution furtherassures insulating property and further increases the reliability of theelectrode.

In the through electrode according to the present invention, the throughplug may include a barrier film covering a side wall inside the throughhole, and a metal film around covered by the barrier film. In thepresent invention, the barrier film serves as an insulating film thatprevents diffusion of a metal component contained in the metal film intooutward of the through plug. Such configuration effectively prevents thediffusion of a metal component in the metal film into the semiconductorsubstrate.

According to the present invention, there is provided a method ofmanufacturing a through electrode, comprising forming a hole on onesurface of a silicon substrate; forming an insulating film that coversthe surface and an inner wall of the hole; forming a conductive film soas to fill the hole; performing polishing or etching back on theconductive film so as to remove a portion of the conductive film formedoutside the hole for exposing the insulating film, and to retreat asurface of the conductive film into an inner level of the siliconsubstrate than the surface thereof, for forming a conductive plug and arecessed portion; growing a metal film on a retreated surface of theconductive plug thus to fill the recessed portion and to further form abump having a larger diameter outside the hole than that of a portion ofthe bump located inside the hole; and polishing another surface of thesilicon substrate for exposing the conductive plug, thus to form athrough electrode.

The method of manufacturing thus arranged includes retreating thesurface of the conductive film into an inner level of the siliconsubstrate than the surface thereof, thus to form the recessed portion,that is, the retreated portion on the surface of the silicon substrate,thereby forming a height gap on these surfaces. Therefore, such recessedportion assures the connection of the conductive plug and the bump.Also, such method eliminates the need to form an insulating film on thesilicon substrate surface and to form an opening thereon at a determinedposition, when forming the bump. Accordingly, a through electrode thatoffers excellent property can be stably manufactured through asimplified process, and hence a manufacturing cost is decreased.

In the present invention, the insulating film may be formed as a thickfilm. Such configuration further assures the insulation between thethrough electrode and the silicon substrate, and the prevention ofgeneration of a parasitic capacitance in the silicon substrate.

In the method of manufacturing according to the present invention,forming the bump may include growing the metal film selectively on theretreated surface of the conductive plug. Having such process, theconfiguration of the bump, which effectively has adhesion between thebump and the through plug, may be further obtained by an anchoringeffect.

In the method of manufacturing according to the present invention,forming the bump may include forming a barrier metal film on the surfaceof the conductive plug and a side wall of the recessed portion, andgrowing the metal film utilizing the barrier metal film as the base.Such method further assures the electrical contact between theconductive plug and the bump. Also, the metal film may be more assuredlygrown from the surface of the conductive plug and the side surface ofthe recessed portion. Accordingly, a stability of manufacturing the bumpmay be increased.

The method of manufacturing according to the present invention maycomprise, after forming the conductive plug, selectively removing aportion of the silicon substrate from another surface thereof oppositeto the one surface thus to expose a surface of the conductive plug; andgrowing another metal film on an exposed surface of the conductive plug,thus to form a bump on the rear surface.

Alternatively, the method of manufacturing according to the presentinvention may comprise, after forming the through electrode, growinganother metal film on an exposed surface of the conductive plug, thus toform a bump on the rear surface.

In the present invention, since the inner wall of the hole is coveredwith the insulating film, the bump on the rear surface may be formedwithout additionally forming another insulating film for forming thebump on the rear surface, that is, another surface of the siliconinsulator. This allows simplifying the manufacturing process, and hencefacilitating the manufacturing of the through electrode more easily.Here, in the present invention, the metal film from which to form thebump and the metal film from which to form another bump on the rearsurface may be constituted of an identical material or differentmaterials.

In the method of manufacturing according to the present invention,forming the insulating film may include forming a silicon oxide film onthe one surface of the silicon substrate. Such method further assuresinsulation and protection of the surface of the silicon substrate. Inaddition, such method further ensures suppression of generation of aparasitic capacitance in the silicon substrate along the side peripheryof the through hole.

The method of manufacturing according to the present invention maycomprise forming a barrier film on the one surface of the siliconsubstrate provided with the hole, after forming the insulating film andbefore forming the conductive film. Such method allows effectivelyinhibiting the conductive material in the conductive film from diffusinginto the silicon substrate.

According to the present invention, there is provided a silicon spacercomprising the through electrode.

According to the present invention, there is provided a method ofmanufacturing a silicon spacer, comprising forming a through electrodeby the foregoing method of manufacturing the through electrode.

The silicon spacer according to the present invention includes thethrough electrode formed as specified above. Accordingly, the conductiveplug and the bump are tightly adhered to each other, and an electricalconductive path is adequately secured in a cross-sectional direction ofthe silicon substrate. Therefore, such spacer can be advantageouslyprovided between a plurality of semiconductor devices to bethree-dimensionally stacked, for assured electrical connection betweenthose devices.

As described above, the present invention provides a through electrodethat offers excellent property and can be manufactured through a simpleprocess, wherein a through plug formed by embedding a conductivematerial in a through hole penetrating a silicon substrate and a bumpare connected with the through plug inside the through hole, and thebump has a larger-diameter portion outside the through hole.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, advantages and features of the presentinvention will be more apparent from the following description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view showing a configuration of asilicon spacer according to an embodiment of the present invention;

FIGS. 2A to 2C are schematic cross-sectional views for explaining amanufacturing process of the silicon spacer of FIG. 1;

FIGS. 3D to 3F are schematic cross-sectional views for explaining amanufacturing process of the silicon spacer of FIG. 1;

FIGS. 4G and 4H are schematic cross-sectional views for explaining amanufacturing process of the silicon spacer of FIG. 1;

FIG. 5I is a schematic cross-sectional view for explaining amanufacturing process of the silicon spacer of FIG. 1;

FIGS. 6A and 6B are schematic plan views and cross-sectional viewsshowing a constitution of through electrodes;

FIG. 7 is a schematic cross-sectional view showing a configuration of asemiconductor device including a silicon spacer, according to theembodiment;

FIG. 8 is a schematic cross-sectional view showing a configuration of asilicon spacer according to a comparative example;

FIGS. 9A to 9C are schematic cross-sectional views for explaining amanufacturing process of the silicon spacer according to the comparativeexample;

FIGS. 10D to 10F are schematic cross-sectional views for explaining amanufacturing process of the silicon spacer according to the comparativeexample; and

FIGS. 11G and 11H are schematic cross-sectional views for explaining amanufacturing process of the silicon spacer according to the comparativeexample.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be now described herein with reference toillustrative embodiments. Those skilled in the art will recognize thatmany alternative embodiments can be accomplished using the teachings ofthe present invention and that the invention is not limited to theembodiments illustrated for explanatory purposed.

Firstly, a spacer provided with a through electrode according to thepresent invention will be described. The spacer is to be disposedbetween three-dimensionally stacked semiconductor devices formed on asubstrate, for securing an electrical connection.

FIG. 7 is a schematic cross-sectional view showing a configuration of asemiconductor device on which a plurality of chips is stacked. Thesemiconductor device 60 shown in FIG. 7 includes an MPU/ASIC chip 71, alarge capacitance system memory chip 72, and a 128MNOR flush memory chip73 stacked in this sequence on a base substrate 61, and the substrate 61and the chip 71 are connected via a bonding wire 67, and the substrate61 and the chip 73 are connected via a bonding wire 65.

Normally the semiconductor chip on the second layer from the basesubstrate is required to be smaller in dimensions than that on the firstlayer from the base substrate, in order to secure a room for disposingthe bonding wire for connection, which naturally imposes a limitation toa capacitance and property of the semiconductor chip to be stacked.

However, even when the second layer chip 72 is larger than the firstlayer chip 71 as shown in FIG. 7, interposing a spacer 11 therebetweenand thus connecting electrodes via through electrode 5 generates a spacebetween the first layer chip 71 and the second layer chip 72, therebyallowing disposing the bonding wire 67 for the connection.

The spacer according to the present invention, which is provided withthe through electrode, can be advantageously incorporated in suchsemiconductor devices. Hereunder, an embodiment of the spacer includingthe through electrode will be described referring to the drawings. Here,with respect to all the drawings, constituents employed in common willbe given an identical numeral, and the description thereof will beomitted as the case may be. Also, for the purpose of the description ofthe embodiment, a surface of the spacer on which the retreated surfaceof the through plug constituting the through electrode will be referredto as an upper face (surface), and the opposite surface as a lower face(rear face).

FIG. 1 is a schematic cross-sectional view showing a configuration of asilicon spacer according to this embodiment. A silicon spacer 100 shownin FIG. 1 includes a through electrode 102 penetrating a siliconsubstrate 101, which is a semiconductor substrate, from the upper faceto the lower face thereof. Although FIG. 1 shows a configuration inwhich the single silicon substrate 101 includes two through electrodes102, the number of the through electrodes 102 or a position thereof isnot specifically limited, but may be appropriately determined accordingto a configuration of the semiconductor devices to which the siliconspacer 100 is to be incorporated.

On the upper face of the silicon substrate 101 and on the inner sideface of the through hole penetrating the silicon substrate 101, aninsulative thick film 103 is provided in contact with the siliconsubstrate 101. Inside the through hole penetrating the silicon substrate101, the insulative thick film 103, a SiN film 105, and a through plug107 are filled in this sequence. Accordingly, the side wall of thethrough plug 107 is covered with the insulative thick film 103 via theSiN film 105, thus separated from the silicon substrate 101.

A material for constituting the insulative thick film 103 is to beselected out of those that are stable against treatments to be performedin the manufacturing process of the through electrode 102 to be laterdescribed. Also, preferably the material of the insulative thick film103 is selected material capable of suppressing generation of aparasitic capacitance in the silicon substrate 101. For example, a SiO₂film or the like is preferably employed. Likewise, a thickness of theinsulative thick film 103 is preferably determined so as to securestability under the manufacturing process of the through electrode 102and to allow suppressing generation of a parasitic capacitance. Whenemploying the SiO₂ film as the insulative thick film 103, a thicknessthereof may be, for example, from 300 nm to 5 μm. With a thickness of300 nm or greater, degradation of the through electrode 102 during themanufacturing process can be effectively prevented. Accordingly,emergence of a leak current, caused by a contact of the siliconsubstrate 101 and the first bump 111 or the second bump 115, can besecurely prevented. With a thickness of 5 μm or less, the silicon spacer100 and the through electrode 102 can be formed to be smaller andthinner.

The through electrode 102 includes the through plug 107, an under bumpmetal film 109, a first bump 111, a second bump 115, and a SiN film 105.The through plug 107 serves as a conductive material embedded inside thethrough hole formed in the silicon substrate 101. A material of thethrough plug 107 may be a metal such as copper. The first bump 111 isformed in contact with the upper face of the through plug 107 via theunder bump metal film 109.

The SiN film 105 serves as a barrier film covered on the side wall ofthe through plug 107, for preventing diffusion of a metal component inthe through plug 107 into the insulative thick film 103 and the siliconsubstrate 101. The barrier film may be formed of a material other thanthe SiN, as long as it is an insulative material. Here, the SiN film 105is thinner than the insulative thick film 103. A thickness of the SiNfilm 105 may be, for example, 10 nm or greater. Such thickness assuresproper property of the barrier film.

The upper face of the through plug 107 is located at an inner levelinside the through hole, than an interface between the silicon substrate101 and the insulative thick film 103, thus forming a height gap 113between those faces. The retreated space of the through plug 107 isfilled with a portion of the first bump 111, by which the through plug107 is in contact with the first bump 111 at the retreated face from theinterface between the silicon substrate 101 and the insulative thickfilm 103, that is, at the recessed portion. The first bump 111 isoutwardly expanding outside the through hole in an eaves-like shape,forming an approximately T-shaped cross section. In other words, adiameter of the first bump 111 located outside the through hole islarger than a diameter of the first bump 111 located inside the throughhole. The first bump 111 may be constituted of a metal, such as Au.

The second bump 115 is disposed in contact with the lower face of thethrough plug 107. The second bump 115 is formed within the contact facebetween the insulative thick film 103 and the silicon substrate 101.Accordingly, the second bump 115 is securely kept from making anelectrical connection with the silicon substrate 101. The second bump115 may be constituted of a metal, such as Ni. The second bump 115 maybe provided with a metal coating layer such as Au, on the surfacethereof.

A method of manufacturing the silicon spacer 100 will now be described.FIGS. 2A to 2C, 3D to 3F, 4G, 4H, and FIG. 5I are schematiccross-sectional views showing the manufacturing process of the siliconspacer 100.

Firstly, a photoresist is applied to a surface of the silicon substrate101, and photolithography is performed to form a resist pattern in whichan opening is formed at a position corresponding to the through plug107. Then etching is performed utilizing the resist pattern as a mask,to remove a portion of the silicon substrate 101, thus to form anopening 117 (FIG. 2A).

After removing the photoresist, the insulative thick film 103 is formedall over the upper face of the silicon substrate 101, including theopening 117 (FIG. 2B). The insulative thick film 103 may be an SiO₂ filmdeposited by a CVD technique. Then the SiN film 105, which is to serveas a barrier film, is formed all over the upper face of the siliconsubstrate 101 on which the insulative thick film 103 is provided, in athickness of for example 50 nm by a plasma CVD technique (FIG. 2C).

Thereafter, a seed Cu film (not shown in the drawings) is formed on theSiN film 105. Then electrolytic plating is carried out to completelyfill the opening 117 with a Cu film, and annealing is performed to growthe grains of Cu. At this stage, formation of the Cu film 119 iscompleted (FIG. 3D).

The above is followed by a CMP (Chemical Mechanical Polishing) process,by which the Cu film 119 and the SiN film 105 are removed from the upperface of the silicon substrate 101. Here, conditions of the CMP processare selected such that the upper face of the Cu film 119 falls to anlower level than the contact face between the silicon substrate 101 andthe insulative thick film 103 (FIG. 3E). Specifically, slurry is to beappropriately selected such that the chemical polishing due to theoxidation of the Cu film 119 takes place with priority to the mechanicalpolishing of the insulative thick film 103.

Accordingly, the Cu film 119 is polished with priority while leaving theinsulative thick film 103 not removed on the silicon substrate 101, thusforming the height gap 113 (recess) between the upper face of the Cufilm 119 and the interface between the silicon substrate 101 and theinsulative thick film 103. In this way a recessed portion 131 is definedin a portion of the opening 117, by depressing the Cu film 119 such thatthe upper face thereof is located lower than the upper face of theinsulative thick film 103. Therefore a bottom portion of the recessedportion 131 corresponds to the retreated face, that is, the recessedsurface. Slurry for metal polishing may be employed as such polishingslurry.

Then, a TiW film, which is to serve as the under bump metal film 109,and a resist film 121 are applied all over the substrate 101, andphotolithography is performed to form an opening 123, thus to expose theunder bump metal film 109 (FIG. 3F). The opening 123 is located abovethe through plug 107 as well as the SiN film 105 and the insulativethick film 103 disposed along the side wall of the through plug 107.

Now electrolytic plating is performed to selectively grow an Au filmbased on the exposed portion of the under bump metal film 109. The Aufilm is grown so as to fill the recessed portion 131 and to expand itsdiameter outside the recessed portion 131, thus to form the first bump111 that contacts with the insulative thick film 103. The resist film121 is removed. After that, wet etching is performed utilizing the firstbump 111 as a mask, to thereby remove the under bump metal film 109except a portion formed in the formation region of the first bump 111(FIG. 4G).

Then the surface of the silicon substrate 101 on which the first bump111 is provided is adhered to a supporting component 125, via anadhesive 120 and a peeling layer 122 (FIG. 4H). The adhesive 120 may beof a UV-setting material or a thermosetting material. For the peelinglayer 122, a material having a different absorption wavelength from thatof the adhesive 120, which foams when irradiated by a light of suchabsorption wavelength. Also, the supporting component 125 may beconstituted of a material resistant against heat, chemicals, an externalforce and the like to be applied thereto during a thinning process ofthe silicon substrate 101 such as rear face grinding, to be laterdescribed. Examples of such material include quartz and a glass such asPyrex™, though a material other than glass may be employed, including aplastic such as acrylic resin.

Thereafter, the rear face of the silicon substrate 101 is ground (FIG.5I). The rear face grinding is performed mechanically. A thickness ofthe silicon substrate 101 after the grinding may be set as for example50 to 200 μm, depending on the stack configuration of the semiconductordevice in which the silicon spacer 100 is to be incorporated.

Then non-electrolytic plating is performed to grow a Ni film on theexposed portion of the through plug 107. Here, the growing condition ofthe Ni film is adjusted such that the Ni film is formed in an innerregion than the contact face between the insulative thick film 103 andthe silicon substrate 101, provided on the side wall of the through plug107. The Ni film is then plated with Au on its surface. At this stage,the second bump 115 is formed on the other face of the through plug 107.

Upon peeling the supporting component 125 from the silicon substrate101, the supporting component 125 is removed and the silicon spacer 100as shown in FIG. 1 is obtained.

Now the advantageous effect of the silicon spacer 100 shown in FIG. 1will be described.

In the silicon spacer 100, the surface of the through plug 107 filled inthe through hole of the silicon substrate 101 is located lower in thethrough hole than the interface between the silicon substrate 101 andthe insulative thick film 103, and a height gap 113 is defined betweenthe upper face of the through plug 107 and the contact face between thefirst bump 111 and the insulative thick film 103. Also, a portion of thefirst bump 111 is embedded inside the through hole. The first bump 111has a larger diameter outside the through hole than a diameter insidethe through hole, forming an eaves-like projecting shape.

Such configuration of the bump 111, as being connected to the throughplug 107 inside the through hole and having a larger diameter outsidethe through hole than a diameter inside the through hole, provokes ananchoring effect which enhances and stabilizes the adhesion between thebump 111 and the through plug 107. Also, a sufficiently large contactarea between the through plug 107 and the first bump 111 providesadequate conductivity therebetween and minimizes a contact resistance.Such configuration also provides stability of the manufacturing process.In addition, because of the presence of the insulative thick film 103, adefect can be effectively prevented, such as emergence of a leak currentfrom the bump 111 on the face of the silicon substrate 101, where is theface of the first bump 111 side.

Further, the height gap 113 can be obtained by appropriately selecting aCMP condition with respect to the Cu film 119. This significantlysimplifies the manufacturing process, and also provides stability of themanufacturing process.

Also, the insulative thick film 103, formed between the through plug 107and the silicon substrate 101 along the side periphery of the throughplug 107, is thicker than the SiN film 105. Accordingly, a parasiticcapacitance is effectively decreased from being generated in the siliconsubstrate 101. Such effect becomes more prominent when the insulativethick film 103 has a thickness of 300 nm or greater.

Also, the insulative thick film 103 for protecting the surface of thesilicon substrate 101 and sustaining the first bump 111 still remainsafter the CMP process so as to contact with the larger-diameter portionof the first bump 111. The insulative thick film 103 is originallyformed to be thick, and maintains a sufficient thickness even after theCMP process. Therefore, the insulation between the first bump 111 andthe silicon substrate 101 can be effectively secured. Such effectbecomes more prominent when the insulative thick film 103 has athickness of 300 nm or greater.

Further, as shown in FIG. 3E, a configuration wherein the surface of thesilicon substrate 101 is insulated except the upper face of the throughplug 107 is obtained after forming the through plug 107 and beforeforming the first bump 111, without forming an insulating film on thesurface of the silicon substrate 101, or forming a resist pattern with aphotoresist for defining an opening on the insulating film at a positioncorresponding to the upper surface of the through plug 107. Accordingly,the configuration that the manufacturing process of the first bump 111can be simplified and the relevant manufacturing cost can be reduced isobtained.

Further, in the silicon spacer, since the insulative thick film 103formed so as to cover the side wall of the through plug 107 issufficiently insulative thick film, the second bump 115 does not surpassthe width of the insulative thick film 103 provided along the sideperiphery of the through plug 107. Accordingly, the insulation betweenthe rear face of the silicon substrate 101 and the second bump 115 canbe effectively secured, without additionally providing an insulatingfilm on the rear surface of the silicon substrate 101 for the insulationtherebetween. Consequently, the configuration that the manufacturingprocess for forming the second bump 115 can be shortened is obtained.

Further, in the silicon spacer 100, as shown in FIG. 2B, the insulativethick film 103 provided on the surface of the silicon substrate 101 andthe insulative thick film 103 that covers the side wall of the throughhole are continuously and integrally formed. Therefore, thisconfiguration can be obtained with a simple process. In the case wherethese insulative thick films 103 are separately formed, the thick filmmay separate in the proximity of a boundary region between the surfaceof the silicon substrate 101 and the side wall of the through hole.However, forming the both insulative thick films 103 as a continuous andintegral film allows preventing such separation, and hence enhances thestability during the manufacturing process.

As described above, the silicon spacer 100 includes the insulative thickfilm 103 on the surface of the silicon substrate 101 as well as on theside wall of the through hole. Accordingly, there is no need to forminsulating films for insulating the silicon substrate 101 from the firstbump 111 and from the second bump 115. Therefore, the configuration hasno an additional process for forming insulating films and has simplicityof manufacturing the configuration. Also, the presence of the height gap113 enhances the adhesion between the through plug 107 and the firstbump 111, thereby increasing the property as the through electrode.

Now, further description will be given regarding the configuration ofthe through electrode 102 provided in the silicon spacer 100 shown inFIG. 1, in contrast with a conventional through electrode in asemiconductor device disclosed in the foregoing H. Yonemura, et al.FIGS. 6A and 6B are schematic cross-sectional views showing aconfiguration of the through electrodes. FIG. 6A shows the configurationof the through electrode according to this embodiment, while FIG. 6Bshows the configuration of the conventional through electrode.

Referring to FIG. 6B, the upper face of a through plug 207 is alignedwith the upper surface of a substrate (dotted line in FIG. 6B) in theconventional through electrode, and it is at this surface that thethrough plug 207 and the first bump 211 are in mutual contact. On theother hand, referring to FIG. 6A, the upper face of the through plug 107is located lower than an interface between the silicon substrate 101 andthe insulative thick film 103 serving as the protective film for thesilicon substrate 101 (dotted line in FIG. 6A) and the height gap 113 isdefined, in the through electrode according to this embodiment. Also, aportion of the first bump 111 is embedded in the recessed portion on thethrough plug 107, thus in contact with the through plug 107. Since thefirst bump 111 is in contact with the upper face of the thick film andthat of the through plug 107, the first bump 111 and the through plug107 are tightly adhered to each other, thus achieving more secureelectrical contact therebetween in comparison with the configurationshown in FIG. 6B.

Further, the configuration of FIG. 6A includes the thick film along theside periphery of the through plug 107, which the configuration of FIG.6B does not have. Therefore, the through electrode according to thisembodiment can decrease a parasitic capacitance more effectively thanthe conventional through electrode can.

Further, referring to FIG. 6B, in the case where the bump 211 has alarger diameter than that of the through plug 207, an additional processbecomes necessary for forming an insulating layer between the substrateand the bump 211. Accordingly, the configuration of FIG. 6A can bemanufactured through a fewer number of process than that required by theconfiguration of FIG. 6B. Therefore, the configuration of the throughelectrode according to this embodiment allows simplifying themanufacturing process and hence reducing the relevant manufacturingcost. In addition, though not shown in FIGS. 6A and 6B, the second bump115 of the through electrode according to this embodiment can also beformed through a fewer number of process, than in the case of theconventional through electrode.

Although the present invention has been described based on an embodimentreferring to the drawings, it is to be understood that the foregoing ismerely an example of the present invention, and that various otherconstitutions may be adopted.

For example, the height gap 113 in the silicon spacer 100 according toFIG. 1 is vertically formed with respect to the surface of the siliconsubstrate 101, while a shape of the height gap 113 is not specificallydetermined but may be otherwise designed, including the shape that isexpanded from the inside of the silicon substrate 101 to the outside ofthe silicon substrate 101. Also, though the retreated face of thethrough plug 107 is oriented in parallel to the surface of the siliconsubstrate 101 according to FIG. 1, the retreated face of the throughplug 107 may be of a concave curved surface. For example, such shape maybe obtained by a dishing effect to form a concave recess on the uppersurface of the through plug 107.

Also, the under bump metal film 109 may be constituted of a refractorymetal such as Ti, Ta other than TiW. For example, Ti, TiN, WN, Ta, TaNor the like are illustrated. In addition, a Ta containing barrier metalincluding layers of TaN and Ta may also be employed. The barrier metalfilm may be formed with sputtering, CVD and the like.

Further, though in FIG. 6A, a circular cylinder shaped through electrode102 is described as an example, the shape of the through electrode 102according to this embodiment is not limited to the circular cylinder,but may be another shape as long as the shape allows formation of theheight gap 113, such as an elliptic cylinder or a rectangular columnhaving substantially the same area upper face as lower face.Alternatively, the through electrode 102 may be a truncated cone, atruncated elliptic cylinder or a truncated pyramid which does not have apointed top. The cylinder shape may include a striped shape extending inone direction.

Further, while the foregoing description represents a configurationwherein the through electrode 102 is formed in the silicon spacer 100 asan example, the through electrode 102 may be applied to various othersemiconductor chip substrates, other than the silicon spacer 100.

EXAMPLE

As the example, the silicon spacer 100 shown in FIG. 1 was manufacturedaccording to the process described referring to FIGS. 2A to 2C, 3D to3F, 4G to 4H and 5I. Here, a SiO₂ film of 300 nm in thickness was formedas the insulative thick film 103. The SiN film 105 was formed to have athickness of 50 nm. The through plug 107 was formed of a Cu film. Also,the silicon substrate 101 was thinned to 200 μm by grinding rear surfaceof the silicon substrate 101. The silicon spacer 100 including thethrough electrode 102 was obtained with highly stability of themanufacturing process and an excellent yield.

COMPARATIVE EXAMPLE

As a comparative example, a silicon spacer including a through electrodewas manufactured through a conventional process. FIG. 8 is a schematiccross-sectional view showing a configuration of the silicon spacermanufactured in the comparative example. Also, FIGS. 9A to 9C, 10D to10F, and 11G to 11H are schematic cross-sectional views for explainingthe manufacturing process of a silicon spacer 200 shown in FIG. 8.Hereunder, the manufacturing process of the silicon spacer according tothe comparative example will be described, focusing on differences fromthe foregoing example.

Firstly, a resist pattern was formed on a surface of a silicon substrate201 by a photolithography technique, and etching was performed utilizingthe resist pattern as a mask on the silicon substrate 201, thus to forman opening (not shown in the drawings). Then the resist pattern wasremoved, and an insulating film 203 and a SiN film 205 was formed inthis sequence all over the surface of the silicon substrate 201 on whichthe opening was provided. A SiO₂ film of 10 nm in thickness was formedas the insulating film 203. The SiN film 205 was also formed in athickness of 10 nm.

Thereafter, a Cu film 219 was formed so as to fill the opening (FIG.9A). Then the Cu film 219, the SiN film 205 and the insulating film 203on the silicon substrate 201 was removed with CMP. At this stage, theCMP condition was adjusted such that a surface of the silicon substrate201 to be exposed and a surface of the through plug 207 were aligned(FIG. 9B).

An insulating film 204 was formed in a thickness of 300 nm on thesurface of the silicon substrate 201, as a cover film. Then a resistpattern was formed on the insulating film 204, and etching wasselectively performed on the insulating film 204 located on the throughplug 207, thus to form an opening 231 (FIG. 9C).

Then a first bump 211 that is connected to the through plug 207 wasformed, through the process described referring to FIGS. 3F to 5I, andthe surface on the side of the first bump 211 was fixed to a supportingcomponent 225 via an adhesive (not shown in the drawings) and a peelinglayer (not shown in the drawings) (FIG. 10D).

After the above, the rear face of the silicon substrate 201 was ground,so as to expose the lower face of the through plug 207. Then siliconetch back on the rear face was performed, thus to form a Cu post 210(FIG. 10E), followed by forming an insulating film 206 all over the rearsurface, as a cover film. As the insulating film 206, a SiN film of 100nm in thickness was formed (FIG. 10F). Thereafter, CMP was performed toselectively remove the insulating film 206 on the rear face of thethrough plug 207, thus to expose the through plug 207 (FIG. 11G).Similarly to the example, non-electrolytic plating was performed to growan Ni film on the exposed surface of the through plug 207, to therebyform a second bump 215 around the through plug 207 (FIG. 11H). Then anAu plated film was formed on the surface of the Ni film, after which thesupporting component 225 was removed, and finally the silicon spacer 200shown in FIG. 8 was obtained.

Since the comparative example did not include the insulative thick film103 unlike the example, the silicon spacer 200 according to thecomparative example required additional process of forming theinsulating film 204 and the insulating film 206 for the insulation ofthe through plug 207 from the first bump 211 and from the second bump215, performing selective etching on the insulating film 204 andselectively removing the insulating film 206, resulting in an increasein the number of process in manufacturing.

It is apparent that the present invention is not limited to the aboveembodiment, that may be modified and changed without departing from thescope and spirit of the invention.

1. A through electrode comprising: a silicon substrate provided with athrough hole; an insulating protective film formed on a surface of saidsilicon substrate with an opening connecting with said through hole; athrough plug formed by embedding a conductive material in said throughhole; and a bump connected to said through plug; wherein said bump isconnected to said through plug inside said through hole, and a portionof said bump located outside said through hole has a larger diameterthan that of a portion of said bump located inside said through hole. 2.The through electrode according to claim 1, wherein a larger-diameterportion of said bump is in contact with said insulating protective film.3. The through electrode according to claim 1, further comprising a sidewall insulating film formed so as to cover a side wall of said throughplug.
 4. The through electrode according to claim 3, wherein said sidewall insulating film and said insulating protective film arecontinuously and integrally formed.
 5. The through electrode accordingto claim 1, wherein said through plug includes a barrier film covering aside wall inside said through hole, and a metal film around covered bysaid barrier film.
 6. A silicon spacer comprising a silicon substrateprovided with said through electrodes according to claim
 1. 7. A methodof manufacturing a through electrode, comprising: forming a hole on onesurface of a silicon substrate; forming an insulating film that coverssaid surface and an inner wall of said hole; forming a conductive filmso as to fill said hole; performing polishing or etching back on saidconductive film so as to remove a portion of said conductive film formedoutside said hole for exposing said insulating film, and to retreat asurface of said conductive film into an inner level of said siliconsubstrate than the surface thereof, for forming a conductive plug and arecessed portion; growing a metal film on a retreated surface of saidconductive plug thus to fill said recessed portion and to further form abump having a larger diameter outside said hole than that of a portionof said bump located inside said hole; and polishing another surface ofsaid silicon substrate for exposing said conductive plug, thus to form athrough electrode.
 8. The method according to claim 7, wherein saidforming said bump includes forming a barrier metal film on the surfaceof said conductive plug and a side wall of said recessed portion, andgrowing said metal film utilizing said barrier metal film as a base. 9.The method according to claim 7, comprising, after said step of formingsaid conductive plug: selectively removing a portion of said siliconsubstrate from said another surface thereof opposite to said one surfacethus to expose a surface of said conductive plug; and growing anothermetal film on an exposed surface of said conductive plug, thus to form abump on the rear surface.
 10. The method according to claim 7,comprising, after said forming said through electrode: growing anothermetal film on an exposed surface of said conductive plug, thus to form abump on the rear surface.
 11. The method according to claim 7, whereinsaid forming said insulating film includes forming a silicon oxide filmon said one surface of said silicon substrate.
 12. The method accordingto claim 7, comprising forming a barrier film on said one surface ofsaid silicon substrate provided with said hole, after said forming saidinsulating film and before said forming said conductive film.